RICHARD TRUETT
Schaeffler group advances the art of the valvetrain

Schaeffler's eRocker uses an electronic solenoid that pushes on the end of the camshaft to change the valve opening events. Photo credit: SCHAEFFLER

Politics and government oversight aside, for automakers and suppliers it's still business as usual in raising the fuel efficiency of cars and light trucks. And Germany's Schaeffler Group made a recent swing through Detroit to showcase its latest fuel-saving technologies.
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Automotive News | September 11, 2018 - 11:57 am EST
Richard Truett is a technology and engineering reporter for Automotive News.

DETROIT -- Despite current efforts to revisit light-vehicle fuel economy standards enacted during the Obama administration, there have been no changes to the law, and there might not be for years, as the wheels of government bureaucracy spin slowly and legal challenges play out.

For automakers, that means it's business as usual, for now, in continuing to meet the stringent rule on the books -- an average 46.7 mpg across an automaker's fleet by 2025.

And so last week in Detroit, Germany's Schaeffler Group rented the conference center of a casino here and invited hundreds of engineers from General Motors, Ford, Fiat Chrysler, Toyota, Nissan and others to take a deep dive into the company's latest fuel-saving technologies.

Judging by the crowd, you'd never know there is an effort by the current administration to hold fuel economy rules at 2020 levels -- 37 mpg. Engineers packed each technical session that highlighted various engine parts and transmission components. Displays that showcased components, such as the Audi e-tron's electric motor and transmission, drew lines of engineers waiting to examine them and to ask the engineers who designed them detailed technical questions.

Schaeffler's electric cam phaser provides more precise level of valve timing adjustment. Photo credit: RICHARD TRUETT

Two valvetrain technologies that Schaeffler engineers have developed deliver significant fuel economy gains for a reasonable cost, the company says.

The first technology, the eRocker system, looks the most promising to me. Numerous automakers already offer engines that have camshafts with two sets of lobes that change the timing and duration of the valve opening based on the engine's speed and load. Or, a switchable cam can be used for cylinder deactivation.

But all of these systems use oil pressure to change the cam lift. It's expensive for a couple of reasons. It greatly complicates engine design because intricate oil passages have to be machined into the cylinder head. The systems also require a more robust oil pump, and they increase an engine's parasitic losses.

Schaeffler's eRocker uses an electronic solenoid that pushes on the end of the camshaft to change the valve opening events. It's brilliantly simple.

The Audi e-tron's electric drivetrain. Photo credit: RICHARD TRUETT

This year, Mary Gustanski, Delphi's chief technical officer, told me an automaker might spend as much as $80 million redesigning a cylinder head's oil circuits to enable a variable cam lift system. That machining is not required for the eRocker, which would cost automakers somewhere between $30 and $70 per camshaft to install.

There would be additional outlays for the software to operate the solenoid, but that cost is far lower than redesigning a cylinder head and modifying an engine plant.

The other interesting valvetrain technology involves cam phasing -- adjusting the timing of when the valves open by rotating the camshaft sprocket forward or backward slightly. Most of today's cam phasers use hydraulic pressure -- oil -- to adjust valve timing. Those adjustments are based on the speed and load of the engine and improve efficiency.

But, as with oil-driven adjustable camshafts, hydraulic cam phasers have shortcomings. When oil is cold, for example, reaction time is slow. And oil-fed cam phasers also increase parasitic losses. Another issue is that engine designers have increased engine efficiency by reducing oil pressure. That can affect cam phaser performance.

Schaeffler engineers have developed a fast-acting electric motor and gear-driven cam-phasing system that fits in place of hydraulic phasers. Schaeffler's electric cam phasers enable all sorts of improvements.

For example, when the engine is turned off, the phasers cam move the camshaft to the optimal position for a faster, smoother restart.That can't happen with a hydraulic system because there's no oil pressure when the engine isn't running. The electric phasers are unaffected by temperature, and they react faster than hydraulic systems.

Combined, the two systems could yield fuel economy gains on some engines of about 15 percent or more, Schaeffler says.

The race to improve fuel economy in gasoline and diesel engines goes on and will continue, no matter who's in the White House. Globally, emissions standards are tightening, and engine designers are now turning their attention to designing internal combustion engines that are designed to work with an electrified powertrain.

The internal combustion engine, I'm convinced, won't die soon, but it will be smaller and more efficient.

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